E-Bike Torque Sensing With Contactless Signal Transfer
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Solution Overview
Problem
Existing torque sensors for electric bicycles face challenges in accurately measuring torque due to the lack of a direct path between the control electronics and the rider input shaft, particularly in drive systems where the motor is concentric to the rider input axle, leading to errors in torque calculation.
Innovation Solution
A torque sensor system incorporating a contact sensor and a contactless sensor, where the contact sensor measures torque applied to an output component rotated by an electric motor, and the contactless sensor provides an output signal proportional to the input signal, using a one-way clutch and strain gauges to accurately measure torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the motor is positioned concentric with the rider input axle to achieve compact drive system design, then the device complexity is reduced and space is saved, but the measurement precision of torque at the rider input interface deteriorates due to lack of direct access path
Solution Approach 1:
The patent introduces a magnetic coupling intermediary system between the rider input axle and the sensor. Magnets are attached to the rotating output component, and corresponding magnetic sensors are positioned on the stationary housing, creating a non-contact measurement path that transmits rotational information without mechanical connection.
Solution Approach 2:
The patent replaces direct mechanical contact between the sensor and rotating components with a magnetic field-based measurement system. This substitution eliminates the need for physical access to the rider input axle while maintaining measurement capability through magnetic coupling between rotating magnets and stationary sensors.
2Measurement precision
If a contact sensor is used to measure torque directly on the rotating output component, then the measurement precision is improved, but the device complexity increases due to additional components and installation requirements
Solution Approach 1:
The patent replaces complex mechanical contact sensors with simpler magnetic sensors that detect magnetic field changes. This substitution maintains measurement precision while reducing mechanical complexity, as magnetic sensors require no physical contact, lubrication, or complex mounting on rotating parts.
Solution Approach 2:
The magnetic field serves as an intermediary between the rotating output component and the stationary sensor, enabling torque measurement without direct mechanical contact. This intermediary approach simplifies the sensor system by eliminating mechanical linkages while preserving measurement accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides precise torque measurements suitable for drive systems with a motor input concentric to the rider input shaft, enabling proportional control of the electric pedal assist motor and automatic shifting based on riding scenarios.
Implementation Method 1
A non-rotatable outer transformer coil is radially spaced apart from and surrounds the inner transformer coil
Implementation Method 2
a radio transmitter is coupled to and rotatable with the output component about the axis, while a radio receiver, in communication with the transmitter, is spaced apart from the transmitter and is not in physical contact with the output component
Data Source
AI summary
A torque sensor includes a contact sensor and a contactless sensor. An electric drive system for a bicycle includes an electric motor having a rotor rotatable about an axis. An output component is coupled to the electric motor and is rotatable about an axis. An input component is rotatable about the axis and is concentric with the output component and the rotor. A one-way clutch is disposed between the input component and output component. The contact sensor is coupled to the output component. The contact sensor is configured to measure a torque applied to the output component by the input component and provide an input signal. The contactless sensor is disposed between the output component and a fixed component. The contactless sensor is configured to provide an output signal proportional to the input signal.